Data communication
Myth vs fact
Myth: Fibre sends data at the speed of light
Your fibre internet is not moving at the speed of light. Here is why.
Quick check · tap an answer to continue
Lesson notes
Key points
- Light in glass slows down because the core's refractive index is about 1.5, so signals travel roughly two thirds of light speed in vacuum.
- Copper is not far behind, since electrical signals in cable also propagate at a large fraction of light speed, so fibre wins on bandwidth, not propagation speed.
Myth: Fibre optic cables carry data at the speed of light in vacuum
Fact: Light in fibre travels about two thirds as fast; fibre's edge is bandwidth
Takeaway: Fibre is wider, not dramatically faster, than copper.
Quick check: Myth or fact: fibre beats copper mainly by offering more bandwidth.
- Myth
- Fact
- Depends
Both propagate near similar speeds; fibre's advantage is bandwidth and low attenuation.
Refractive indexPropagation speed
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